Expressing the genome in bacterial cells.

Bacteria are prokaryotes—single-celled organisms that lack a nucleus. Because no nuclear membrane separates a bacterium’s genome from ribosomes and other cellular contents, protein synthesis can start before an mRNA transcript is complete. Bacterial genes do not have introns (noncoding regions of DNA). Thus editing mRNA transcripts, which involves removing introns prior to protein synthesis, is not needed. (via Gateway to U.S. DOE Biological and Environmental Research Image Galleries)